Method and system for airborne missile guidance

ABSTRACT

A method and system for directing a missile to a target in which a targeting vehicle measures range to the target and to the missile and also measures the angle between the line of sight to the target and the line of sight to the missile. A computed angle between lines of sight from the missile to the target and to the vehicle is derived from the measured ranges and measured angle and is transmitted to the missile. The missile receives the transmitted angle information and provides an output indicative of a measured angle between the line of sight to the targeting vehicle and the missile velocity vector. The computed angle information received by the missile is compared with the measured angle to provide an error signal for controlling missile steering fins.

Unite States atet ueene Se t. 2 1975 y P METHOD AND SYSTEM FOR AIRBORNE MISSILE GUIDANCE Primary Examiner-Verlin R. Pendegrass [75] Inventor: Paul J. Queeney, Baltimore, Md. Attorney Agent or Flrm D' Schron [73] Assignee: Westinghouse Electric Corporation, [57] ABSTRACT Pittsburgh A method and system for directing a missile to a tar et g [22] Filed. Jam 15 1974 in which a targeting vehicle measures range to the tar- Appl. No.: 433,597

get and to the missile and also measures the angle between the line of sight to the target and the line of sight to the missile. A computed angle between lines of sight from the missile to the target and to the vehicle is derived from the measured ranges and measured angle and is transmitted to the missile. The missile re ceives the transmitted angle information and provides an output indicative of a measured angle between the line of sight to the targeting vehicle and the missile velocity vector. The computed angle information received by the missile is compared with the measured angle to provide an error signal for controlling missile steering fins.

6 Claims, 3 Drawing Figures PATENTEDSEP 2W5 3,902,884

30\ I Rl Rz, y A RADAR AN TRANSMITTER 5: STEM l.

METHOD AND SYSTEM FOR AIRBORNE NIISSILE GUIDANCE BACKGROUND OF THE INVENTION 1. Field of the Invention This invention relates to missile guidance systems, and more particularly to a method and control means for guiding an airborne missile to a target in response to radar returns.

2. State of the Prior Art In order to guide a missile to a target, information must be provided to the guided missile to enable the guided missile at some point in time to reach the same position as the target. Many different arrangements, often complicated, have been provided to perform this function. For example, in one prior system, a control center including a radar system first measures the direction and velocity of a target and then separately measures the direction and velocity of a guided missile. The calculation is made of the velocity and direction the missile will have to assume to intercept the target, and control signals indicative of the error between actual missile direction and desired missile direction are communicated to the missile for guidance. Such systems require many measurements to be performed, increasing the cost and complexity of the necessary equipment. This is particularly significant in view of the fact that equipment included on the missile is not reusablev Further, additional complexity of systems decreases reliability and increases size. In free-falling missiles such as bombs, the additional size may be an important factor.

OBJECTS AND SUMMARY OF THE INVENTION It is therefore an object of the present invention to provide a novel method and guided missile system in which a minimal number of measurements are performed to obtain the information necessary for missile guidance.

It is also an object of the present invention to provide a novel system of the type described which is simpler in construction than typical prior art system.

It is another object of the present invention to provide a novel missile guidance method and guided missile system in which the missile need not include equipment generating a spatial reference.

It is also an object of the present invention to provide a novel method for providing a control signal for missile guidance.

A system is disclosed for directing a missile toward a target using a targeting vehicle. The targeting vehicle includes: means for measuring the range from the targeting vehicle both to the target and to the missile and for measuring the angle between a line of sight from the targeting vehicle to the target and a line of sight from the targeting vehicle to the missile; means for deriving a computed angle indicative of an angle between the line of sight from the targeting vehicle to the missile and a line of sight from the missile to the target in response to said range and angle measuring means; and, means for transmitting to said missile a signal indicative of said computed angle.

The missile includes: an array of antennas carried by the missile with the axes of said array having a predetermined orientation with respect to a velocity vector of said missile; a receiver coupled to said antenna array for receiving from said transmitting means the signal indicative of said calculated angle; measuring circuit means coupled to said receiver for measuring the angle of reception of said computed angle indicative signal from said target vehicle with respect to axes of said antenna array for providing a signal indicative of a measured angle between the velocity vector of said missile and a line of sight from said missile to said targeting vehicle; means for comparing signals indicative of said measured angle and said computed angle; and, means responsive to said comparing means for controlling the direction of said missile, whereby said missile is directed toward the target.

BRIEF DESCRIPTION OF THE DRAWINGS The means by which the foregoing objects and features of novelty are achieved are pointed out with particularity in the claims forming the concluding portion of the specification. The invention, both as to its organization, and manner of operation may be further understood by reference to the following description taken in connection with the following drawings in which:

FIG. 1 is an illustration of the present system illustrating the relative positions of a targeting vehicle, guided missile and a target;

FIG. 2 is further illustrative of a guided missile included in the system of the present invention; and,

FIG. 3 is a block diagrammatic representation of a system constructed in accordance with the present invention.

DETAILED DESCRIPTION Referring now to FIG. 1 there is provided a targeting vehicle 10 and a guided missile 12 for intercepting a target 14. The targeting vehicle 10 may be a manned aircraft and the missile 12 may be launched from the targeting vehicle or from another location. In accordance with the illustrated embodiment, the missile may be a free-falling bomb without its own propulsion system and may be dropped from the targeting vehicle 10 and directed to a target as is hereinafter described.

There is a first line of sight between the targeting vehicle 10 and the target 14 designated R1. To facilitate the description, the line of sight R1 is also used hereinafter to designate the range from the targeting vehicle 10 to the target 14. A second line of sight between the targeting vehicle 10 and the missile 12 is designated R2, and the designation R2 is also used hereinafter to designate the range from the targeting vehicle 10 to the missile 12. As shown in FIG. 1 and used hereinafter in connection with the description of operation of the system with respect to FIG. 3, an angle 6 is a measured angle between the lines of sight R1 and R2; y is a computed angle, computed in a manner described below, between the line of sight R2 and a line of sight R3 from the missile 12 to the target 14; ,8 is a measured angle between a velocity vector V of the missile 12 and the line of sight R2.

Referring now to FIG. 2, the missile 12 is illustrated in part in greater detail. The missile 12 includes a weather vane assembly 16 which is carried by the missile 12, for example, in the nose of the missile, to act literally as a weather vane. As is described hereinafter, the weather vane assembly 16 is aerodynamically designed so that the missile moves through the air, the weather vane assembly 16 points directly into the air moving past the missile. This insures that the axis 18 of the assembly 16 is substantially parallel to and preferably coincident with the velocity vector V or the missile 12.

The weather vane assembly 16 may include a central shaft or elongated cylindrical body 20 having antenna arrays 22 on a front portion mounted about the central axis 18 and an electronic unit 24 in a rear portion. The arrays 22 comprise conventional antennas, e.g., welll n own two inch diameter ferrite arrays, and are preferably positioned such that one antenna array is included in each quadrant of the shaft 20. The arrays 22 in the preferred forms comprise well-known monopulse or interferometer arrays having directional characteristics. The directional axes of the antenna arrays 22 have a predetermined orientation with respect to the central axis 18 of the assembly 16 and thus a predetermined orientation with respect to the velocity vector V of the missile. This predetermined orientation may be, for example, 90. The electronics unit 24 components are illustrated and described hereinafter further in connection with FIG. 3.

The weather vane unit 16 may include an outer cylinder 26 attached to the central shaft 20 by means of struts 28. The weather vane unit 16 is movably anchored on the missile 12 preferably such that when the missile 12 is in motion, the axis of the shaft 20 is coincident with the velocity vector V of the missile 12. Depending on the mounting of the unit 16 on the missile 12, the central axis 18 of the weather vane unit 16 may be parallel to and slightly displaced from the velocity vector V of the missile 12. However, the difference is negligible with respect to the magnitude of measurements being performed.

The electronic unit 24 and the equipment carried by the targeting vehicle are further illustrated in FIG. 3 wherein the same reference numerals are used to denote elements corresponding to those of FIGS. 1 and 2. The individual functional blocks illustrating components in FIG. 3 perform the designated functions in known manners and may be constructed by those skilled in the art.

The targeting vehicle 10 may include a conventional radar system or any other system or combination of systems capable of determining the range and direction to both the target and the missile. In the illustrated embodiment, range and direction may be determined by a suitable radar system 30. The radar system 30 supplies range and direction information to a computer 32 which in turn supplies a signal indicative of the angle 'y to a transmitter 34. The electronic unit 24 in the missile 12 includes a suitable receiver 36 which is coupled to the antenna arrays 22. Signals from the receiver 36 are coupled to a measuring circuit 38 to generate a signal indicative of the measured angle B in a manner described hereinafter. The receiver 36 also receives the signal transmitted from the targeting vehicle 10 and provides a received signal indicative of the calculated angle y. The calculated angle 'y and the measured angle B are supplied from the respective receiver 36 and measuring circuit 38 to a suitable comparison circuit 40. An output signal from the comparison circuit 40 related to the relative sizes of the angles 'y and B is applied to a control unit 42 included in the missile 12 for controlling steering means such as fins or other steering surfaces.

Operation In accordance with the present invention, the radar system in the targeting vehicle 10 sends out transmitted signals and receives returns from the missile 12 and target 14. From the radar system position and timing data, the angle 6 between the target and missile lines of sight may be computed by conventional means and the ranges R1 and R2 may be conventionally computed. This is sufficient information to define the triangle R1, R2, R3, i.e., the triangle having the vehicle 10, missile 12 and target 14 at its vertices. From this range and angle information, the angle computer 32 derives the computed angle y by conventional trigonometric techniques, e.g., through the use of the law of cosines. The transmitter 34 transmits a signal indicative of y to the missile 12 and the receiver 36 receives input energy from the transmitter 34.

There are sufficient arrays 22 comprised of plural antennas about the periphery of the shaft portion 20 of the weather vane section 16 to insure reception of energy from the targeting vehicle 10 regardless of the orientation of the missile 12 with respect thereto. The receiver 36 may be switched between arrays 22 to locate the array receiving the strongest amplitude signal from the transmitter 34 and may then dwell on that array. This selection function may be performed by suitable switching and comparing means in the receiver 36 or in the measuring circuit 38. One receiver 36 may be used for each array 22 where expense is not prohibitive.

The measuring circuit 38 compares the energy received by the antannas within a selected array 22 to provide a'measurement of the angle of signal reception with respect to the array axis which is oriented at a predetermined angle relative to the velocity vector V, e.g., perpendicular to the velocity vector. This may be accomplished by conventional direction determining means such as interferometer or monopulse processing circuits in the measuring circuit 38. The information as to the angle of reception relative to the array axis and the orientation of the array axis relative to the velocity vector V is combined to provide a signal indicative of the measured angle B which is measured space angle between the velocity vector V and the line of sight to the targeting vehicle 10. The received signal indicative of the angle y and the signal indicative of the measured angle B are supplied to the comparison circuit 40. The comparison circuit 40 measures the difference between the computed angle 'y and the measured angle B to provide an error signal to the control unit 42. The error signal indicates an error between the direction of the vector V and the direction to the target 14 from the missile 12. When the angle B is made to coincide with the angle 'y the velocity vector of the missile 12 is pointed at the target 14.

The error signal from the comparison circuit 40 is applied to the control unit 42 to operate control means such as fins on the missile 12 in order to null errors between the desired computed angle 'y and the measured angle B In a nominal embodiment, 20-30 measurements of B are made each second. Consequently, errors in the measurement of B tend to cancel each other, enhancing system accuracy.

While the transmitter 34 in the targeting vehicle 10 is shown as being separate from the radar system 30, the signal indicative of the angle 'y may be transmitted by encoding the radar signal utilized to obtain the range and direction information. The system for determining direction and range to the missile may be a separate radar or transponder system of any suitable conventional type.

What is thus provided is a system in which a minimal number of measurements are made to insure accurate guidance of a missile to a target. The system of the present invention may be used for guidance of a missile to a target or as a lock-on system. In other words, the system of the present invention could be used when a missile is initially several miles from a target, with terminal guidance being provided by conventional target seeking means. In the present system, circuitry on the missile is simplified since the missile need only measure and correct one angle. The missile need not generate an internal spatial reference for comparison with external position command signals.

The present invention may be embodied in other specific forms without departing from the spirit or essential characteristics thereof. The presently disclosed embodiments are therefore to be considered in all respects as illustrative and not restrictive, the scope of the invention being indicated by the appended claims rather than by the foregoing description, and all changes which come within the meaning and range of equivalency of the claims are therefore intended to be embraced therein.

What is claimed is:

1. A system for directing a missile toward a target comprising, in combination:

a targeting vehicle including,

means for measuring the range from the targeting vehicle both to the target and to the missile and for measuring the angle between a line of sight from the targeting vehicle to the target and a line of sight from the targeting vehicle to the missile;

means for deriving a computed angle indicative of an angle between the line of sight from the targeting vehicle to the missile and a line of sight from the missile to the target in response to said range and angle measuring means; and,

means for transmitting to said missile a signal indicative of said computed angle;

the missile including:

an array of antennas carried by the missile with the axes of said array having a predetermined orientation with respect to a velocity vector of said missile;

a receiver coupled to said antenna array for receiving from said transmitting means the signal indicative of said calculated angle;

measuring circuit means coupled to said receiver for measuring the angle of reception of said computed angle indicative signal from said target vehicle with respect to axes of said antenna array for providing a signal indicative of a measured angle between the velocity vector of said missile and a line of sight from said missile to said targeting vehicle;

means for comparing signals indicative of saiad said angle and said computed angle; and,

means responsive to said comparing means for controlling the direction of said missile, whereby said missile is directed toward the target.

2. The combination of claim 1 wherein said array of antennas is mounted on a weather vane unit and includes a plurality of antenna arrays spaced on quadrants of said weather vane unit, said receiver in said missile including means for selecting reception from one of said plurality of antenna arrays receiving the highest amplitude signal from the transmitting means in said targeting vehicle.

3. The system of claim 2 wherein said range and angle measuring means includes a radar system operable to track said target.

4. The system of claim 1 wherein said range and angle measuring means includes a radar system operable to track said target.

5. A system for guiding a missile toward a target from a targeting vehicle comprising:

means for measuring a first angle between a missile line of sight and a target line of sight from the targeting vehicle and for measuring the ranges to the target and to the missile from the targeting vehicle;

means for calculating'an angle between a target line of sight and a targeting vehicle line of sight from the missile in response to said measured first angle and ranges;

means for measuring a second angle between a velocity vector of the missile and the targeting vehicle line of sight from the missile; and,

means for modifying the direction of the missile in response to said calculated angle and said measured second angle.

6. A method for giiding a missile toward a target comprising the steps of:

a. measuring a first angle between a missile line of sight and a target line of sight from a targeting vehicle;

b. measuring the ranges to the target and the missile from the targeting vehicle;

c. calculating an angle between a target line of sight and a targeting vehicle line of sight from the missile in response to said measured first angle and ranges;

cl. measuring a second angle between a velocity vector of the missile and the targeting vehicle line of sight from the missile;

e. comparing the calculated angle to the measured second angle; and,

f. modifying the direction of the missile in response to the comparison. 

1. A system for directing a missile toward a target comprising, in combination: a targeting vehicle including, means for measuring the range from the targeting vehicle both to the target and to the missile and for measuring the angle between a line of sight from the targeting vehicle to the target and a line of sight from the targeting vehicle to the missile; means for deriving a computed angle indicative of an angle between the line of sight from the targeting vehicle to the missile and a line of sight from the missile to the target in response to said range and angle measuring means; and, means for transmitting to said missile a signal indicative of said computed angle; the missile including: an array of antennas carried by the missile with the axes of said array having a predetermined orientation with respect to a velocity vector of said missile; a receiver coupled to said antenna array for receiving from said transmitting means the signal indicative of said calculated angle; measuring circuit means coupled to said receiver for measuring the angle of reception of said computed angle indicative signal from said target vehicle with respect to axes of said antenna array for providing a signal indicative of a measured angle between the velocity vector of said missile and a line of sight from said missile to said targeting vehicle; means for comparing signals indicative of saiad said angle and said computed angle; and, means responsive to said comparing means for controlling the direction of said missile, whereby said missile is directed toward the target.
 2. The combination of claim 1 wherein said array of antennas is mounted on a weather vane unit and includes a plurality of antenna arrays spaced on quadrants of said weather vane unit, said receiver in said missile including means for selecting reception from one of said plurality of antenna arrays receiving the highest amplitude signal from the transmitting means in said targeting vehicle.
 3. The system of claim 2 wherein said range and angle measuring means includes a radar system operable to track said target.
 4. The system of claim 1 wherein said range and angle measuring means includes a radar system operable to track said target.
 5. A system for guiding a missile toward a target from a targeting vehicle comprising: means for measuring a first angle between a missile line of sight and a target line of sight from the targeting vehicle and for measuring the ranges to the target and to the missile from the targeting vehicle; means for calculating an angle between a target line of sight and a targeting vehicle line of sight from the missile in response to said measured first angle and ranges; means for measuring a second angle between a velocity vector of the missile and the targeting vehicle line of sight from the missile; and, means for modifying the direction of the missile in response to said calculated angle and said measured second angle.
 6. A method for guiding a missile toward a target comprising the steps of: a. measuring a first angle between a missile line of sight and a target line of sight from a targeting vehicle; b. measuring the ranges to the target and the missile from the targeting vehicle; c. calculating an angle between a target line of sight and a targeting vehicle line of sight from the missile in response to said measured first angle and ranges; d. measuring a second angle between a velocity vector of the missile and the targeting vehicle line of sight from the missile; e. comparing the calculated angle to the measured second angle; and, f. modifying the direction of the missile in response to the comparison. 